What Is a Pipe Offset? What Is a Rolling Offset?
In plumbing, HVAC, and industrial piping, a pipe offset is a change in direction used to route a pipeline around an obstacle or to connect two parallel lines that are not perfectly aligned. When the misalignment occurs in two different directions simultaneously — both horizontally (the set) and vertically (the rise) — it is called a rolling offset, or pipe rolling offset.
A rolling offset requires two angled fittings of the same bend to complete the maneuver: one fitting changes direction at the start of the offset, and a second fitting returns the pipe to its original direction at the end. The diagonal section connecting these two fittings is called the travel, and the straight horizontal distance covered is called the run.
How Do I Use the Rolling Offset Calculator?
- Select your unit system: US Imperial (inches) or Metric (millimeters).
- Enter the Set — the horizontal offset distance between the two parallel pipes.
- Enter the Rise — the vertical offset distance between the two parallel pipes.
- Choose your fitting bend angle from the dropdown (11.25°, 22.5°, 30°, 45°, 60°) or select "Custom" to enter any angle between 0.01° and 89.99°.
- Click Calculate to instantly get:
- True Offset — the diagonal distance across both offsets combined.
- Travel — the length of pipe needed to complete the offset.
- Run — the horizontal distance the pipeline advances during the offset.
- Offset Multiplier — use it to quickly find travel from true offset.
How Do I Calculate the Pipe Rolling Offset?
A rolling offset forms an imaginary rectangular box. The set and rise are two legs of a right triangle, and the true offset is the hypotenuse of that triangle. Once you know the true offset, you apply a second right triangle using the bend angle of the fitting to find the travel and run.
Step 1 — Find the True Offset
Use the Pythagorean theorem:
True Offset = √(Set² + Rise²)
Example: Set = 6 in, Rise = 8 in → True Offset = √(36 + 64) = √100 = 10 in
Step 2 — Find Travel and Run
Using trigonometry with the fitting bend angle θ:
Travel = True Offset ÷ sin(θ) Run = True Offset ÷ tan(θ)
Example at 45°: Travel = 10 ÷ sin(45°) = 10 ÷ 0.7071 = 14.14 in, Run = 10 ÷ tan(45°) = 10 ÷ 1.0000 = 10.00 in
How to Do a 45-Degree Rolling Offset — Sample Calculation
A 45° bend is the most commonly used fitting for rolling offsets. For 45° fittings,
sin(45°) = √2/2 ≈ 0.7071, so the offset multiplier is 1 ÷ 0.7071 ≈ 1.4142.
Problem: A pipe must clear an obstacle with a set of 9 inches and a rise of 12 inches. What is the travel needed using 45° fittings?
- True Offset = √(9² + 12²) = √(81 + 144) = √225 = 15 in
- Travel = 15 × 1.4142 = 21.21 in
- Run = 15 ÷ tan(45°) = 15.00 in
How Do I Figure Rolling Offset in Piping Fast? — Pipe Offset Multipliers
To speed up field calculations, pipefitters use a pipe offset multiplier table. Multiply the true offset by the multiplier for the fitting in use to get the travel length directly.
| Fitting Bend | Angle | Offset Multiplier (Travel / True Offset) |
|---|---|---|
| 1/32 bend | 11.25° | 5.1258 |
| 1/16 bend | 22.5° | 2.6131 |
| 1/12 bend | 30° | 2.0000 |
| 1/8 bend | 45° | 1.4142 |
| 1/6 bend | 60° | 1.1547 |
Formula: Multiplier = 1 ÷ sin(angle)
Frequently Asked Questions
What is the difference between a simple offset and a rolling offset?
A simple offset shifts a pipe in only one plane (either horizontally or vertically). A rolling offset shifts a pipe in two planes at once — both horizontally and vertically — which is why an imaginary diagonal (the true offset) must be calculated first before finding the travel.
What units does this rolling offset calculator support?
The calculator supports both US Imperial (inches) and Metric (millimeters) unit systems. Simply select your preferred system before entering measurements.
Can I use this calculator for any pipe size?
Yes. The rolling offset calculation is purely geometric and independent of pipe diameter. The results (true offset, travel, run) apply regardless of whether you are working with ½-inch household pipes or 24-inch industrial pipelines.
What bend angles are available?
The calculator includes the most common standard fitting angles: 11.25°, 22.5°, 30°, 45°, and 60°. You can also enter any custom angle between 0.01° and 89.99° for non-standard bends or field-bent pipe.
What is the "true offset" in a rolling offset?
The true offset is the diagonal distance between the centerlines of the two non-parallel pipe sections. It is the hypotenuse of the right triangle formed by the set (horizontal offset) and the rise (vertical offset). All further calculations — travel, run, and multiplier — are derived from the true offset.